The invention reefers to electrically illuminated light panels. Light panels configured for light transmission, such as for illumination of a symbol that is carried on a front face of the light panel, are usually designed as a lighting box that houses one or more light sources and which carries, on a front face of the box, a translucent front panel on which is supported a colored and translucent or light-proof symbol, typically in the form of a colored plastic film. The structural stability of this light panel is provided by the box which is usually manufactured from sheets of metal, whereas the front panel itself lacks inherent stability and torsional rigidity.
Light sources used in light panels are fluorescent lamps, bulbs, light emitting diodes or diode lamps, e.g., to which energy is supplied typically via a connection to the supply mains and which are controlled between switching on and off by means of a timer or a light sensor, e.g.
The front panel is typically made of a translucent and non-transparent acrylic plastic. Acrylic plastic is a homogenous and flexible material that has no directional stability of its own, and which requires support from a rigid supporting frame in order to provide a planar base for a symbol that is to be supported on the front panel. Translucent light panels in sizes which are suitable to be looked at from a greater distance comprise acrylic plastic front panels of considerable weight and thickness, requiring a box of corresponding design and weight in order to support and to stabilize the front panel. This in turn results in raised demands on mounting means and on the surface onto which the light panel is to be mounted. The weight of the conventionally designed light panel is therefore a problem by its own when light panels are mounted on interior walls or brittle building faces, such as plastered house facades, for instance.
The publication of US 2009/0231834 discloses an alternative to the heavy acrylic plastic panel. The document describes a light panel wherein light sources are seated internally in the channels of a channeled plastic sheet. Briefly explained, the channel plastic sheet is a self-supporting structure made of clear plastic having a forward panel that is spaced from a rear panel by means of interconnecting transverse walls that are evenly spaced in a rectangular framework. A disadvantage with this solution is that the intensity of emitted light varies over the area of the light panel, with regions of more intense light where the light sources are located. In order to reduce this problem it is suggested in the document to perform some form of light reducing measures on the front face of the light panel. It will be realized that in order to achieve uniform light distribution over the whole area of the light panel by means of measures provided on the front face of the light panel, such measures need to be adapted so as to produce a stronger light reducing effect in front of the light sources as compared to the regions outside the light sources, thus requiring an intricate tuning of the light reducing measures.
Tests performed by the inventor to the present invention have shown that it will not be sufficient to move the light sources to a position behind the channel plastic sheet in attempt to achieve a uniform light intensity over the whole area of the prior art light panel. This measure will render the light panel look striped, presumably caused by light captured inside the transverse walls which like optic fibers concentrate the light to the forward panel of the channeled plastic sheet.